Where do you all put your external reactors?? On the inflow or outflow side of the canister?? And what is your reasoning????
I finally got my 75 gallon finished and loaded. The first 5 days have gone well with plants/fish/algae. I need to rebuild my reactor. I am probably only getting 50-60% dissolved(even after it goes through my xp3 I am still getting lots of bubble out my spray bar). I made it 12" long, 2" diameter, and had 4-5 bio-balls in it. It is on the intake side of the canister. I am considering putting it on the output side and increasing the size and mayby adding a scrub pad and or more bio-balls in it. My controller is working fine but I have to have a very high bubble count to keep the pH/kH/CO2 close to inline(7.4/21) Yes we have solid water. Any suggestions or ideas would help.

Placing the reactor on the outflow side is supposed to be better for the pump... since they are better in pushing water than pulling it.

What is coming out of your XP3 is probably not even CO2, but O2 instead. I get tiny bubbles every afternoon, with or without CO2, I suppose the water reaches its O2 saturation around that time, and the pressure conditions (high/low/who knows) within the filter pull O2 out of solution.

I don't quite understand the reasoning for adding bioballs etc to the reactor. They are supposed to "smash up bubbles" but I think they just reduce the effective diameter and increase the speed of the water flow, and having an empty reactor chamber slows down the water enough to dissolve the bubbles. I might be totally wrong though and missing a few bits of the puzzle

The bubbles that I see are pretty much constant throughout the day. Our bubble count is somewhere around 3-5 bubbles per second. Its hard to tell at that rate. I am just assumming I am not getting it dissolved because of the constant spray of bubbles out my spray bar, the high bubble count, and my controller never getting below 7.5 pH(7.3 setting) until dark, even at that bubble rate.

I did turn the CO2 off for 15 minutes and to my surprise I did not see a huge reduction in the tiny air bubbles coming from the spray bar. The spray bar still sends out a fairly constant flow of tiny air bubbles. Is this normal??? This is my first canister. One other thing I am using a bio-wheel as well just to add more circulation and O2. I understand they will expel a lot of CO2 but I just thought CO2 was cheap and so what If Ihave to refill 2 or 3 times a year instead of once. I will shut it down for a little while and see if the pH will go lower than 7.5. Anything else??

I too use a Bio-Wheel on my 55 and an XP-3 with an external reactor. It really sounds like your reactor is too small. The one on my 55 gallon tank is around 24" long and 2" in diameter.

And you should run it on the output side for a couple of reasons. First off you want clean water running though it so it doesn't get plugged up and burn up the pump in your cannister filter. Second you want to push the water though it rather than pull it though. Try this experiment. Place your hand over the intake screen of the filter. You will notice very little apparent current flow. Now place your hand over the outflow. Notice the difference? It's the same volume of water (unless you have some kind of strange magic going on there) but the water coming out of the outflow is under pressure.

I would definitely switch the reactor to the output side. I'm becoming more and more a fan of forced diffusion reactors than turbulent reactors. In other words, don't waste your time putting restrictions that slow down flow and drop pressure. Just inject the CO2 into an empty chamber and the pressure that the canister's pump puts out should be enough to cause forced diffusion (similar to how the tap water being under pressure is able to diffuse more gases and releases those gases when sitting at atmospheric pressure).

Is your tank pearling nearer to the end of the day? If so, then the saturated oxygen is coming out of solution in the filter and reactor. That would account for the presence of bubbles coming out of the outtake tube only at the end of the day, as O2 is less soluble in water than CO2. Coupled with the fact that your tank is already super-saturated with O2 at this point so all that excess O2 has no where to go but through the intake and out the outake tube. I am a bit skeptical as that the reactor is being inefficient and the bubbles are CO2 because for a 12.5" reactor, all the CO2 should be dissolved completely unless you're pumping a really really really heavy bubble count. I am curious, what is your bubble rate?

After further monitoring, I think you are right Otherwise....
the dozens of bubbles out the spraybar / second arent CO2, but are probably over-saturated O2 released during pearling...

I guess I wasnt expecting so much pearling. The PH is at 7.0 (14 ppm).

Seriously crazy. 1000's. The bubbles cling to the algae. The bubbles are even sticking to my new Angelfish !! :shock:

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